diff --git a/src/becca/entities/bnote_attachment.js b/src/becca/entities/bnote_attachment.js
index 5ec9cddab..e72faaf6a 100644
--- a/src/becca/entities/bnote_attachment.js
+++ b/src/becca/entities/bnote_attachment.js
@@ -22,8 +22,16 @@ class BNoteAttachment extends AbstractBeccaEntity {
     constructor(row) {
         super();
 
-        /** @type {string} */
-        this.noteAttachmentId = row.noteAttachmentId;
+        if (!row.noteId) {
+            throw new Error("'noteId' must be given to initialize a NoteAttachment entity");
+        }
+
+        if (!row.name) {
+            throw new Error("'name' must be given to initialize a NoteAttachment entity");
+        }
+
+        /** @type {string} needs to be set at the initialization time since it's used in the .setContent() */
+        this.noteAttachmentId = row.noteAttachmentId || `${this.noteId}_${this.name}`;
         /** @type {string} */
         this.noteId = row.noteId;
         /** @type {string} */
@@ -82,6 +90,9 @@ class BNoteAttachment extends AbstractBeccaEntity {
     }
 
     setContent(content) {
+        this.contentCheckSum = this.calculateCheckSum(content);
+        this.save();
+
         const pojo = {
             noteAttachmentId: this.noteAttachmentId,
             content: content,
@@ -99,14 +110,12 @@ class BNoteAttachment extends AbstractBeccaEntity {
 
         sql.upsert("note_attachment_contents", "noteAttachmentId", pojo);
 
-        this.contentCheckSum = this.calculateCheckSum(pojo.content);
-
         entityChangesService.addEntityChange({
             entityName: 'note_attachment_contents',
             entityId: this.noteAttachmentId,
             hash: this.contentCheckSum,
             isErased: false,
-            utcDateChanged: this.getUtcDateChanged(),
+            utcDateChanged: pojo.utcDateModified,
             isSynced: true
         });
     }
@@ -134,6 +143,7 @@ class BNoteAttachment extends AbstractBeccaEntity {
             name: this.name,
             mime: this.mime,
             isProtected: !!this.isProtected,
+            contentCheckSum: this.contentCheckSum,
             isDeleted: false,
             utcDateModified: this.utcDateModified,
             content: this.content,
diff --git a/src/public/app/widgets/mermaid.js b/src/public/app/widgets/mermaid.js
index ad8e94eb8..b4aa7f4f7 100644
--- a/src/public/app/widgets/mermaid.js
+++ b/src/public/app/widgets/mermaid.js
@@ -1,6 +1,7 @@
 import libraryLoader from "../services/library_loader.js";
 import NoteContextAwareWidget from "./note_context_aware_widget.js";
 import froca from "../services/froca.js";
+import server from "../services/server.js";
 
 const TPL = `<div class="mermaid-widget">
     <style>
@@ -76,6 +77,14 @@ export default class MermaidWidget extends NoteContextAwareWidget {
             const renderedSvg = await this.renderSvg();
             this.$display.html(renderedSvg);
 
+            // not awaiting intentionally
+            // this is pretty hacky since we update attachment on render
+            // but if nothing changed this should not trigger DB write and sync
+            server.put(`notes/${note.noteId}/attachments/mermaidSvg`, {
+                mime: 'image/svg+xml',
+                content: renderedSvg
+            });
+
             await wheelZoomLoaded;
 
             this.$display.attr("id", `mermaid-render-${idCounter}`);
diff --git a/src/routes/api/notes.js b/src/routes/api/notes.js
index 5f62e5ae8..11601c481 100644
--- a/src/routes/api/notes.js
+++ b/src/routes/api/notes.js
@@ -127,6 +127,19 @@ function setNoteTypeMime(req) {
     note.save();
 }
 
+function saveNoteAttachment(req) {
+    const {noteId, name} = req.params;
+    const {mime, content} = req.body;
+
+    const note = becca.getNote(noteId);
+
+    if (!note) {
+        throw new NotFoundError(`Note '${noteId}' doesn't exist.`);
+    }
+
+    note.saveNoteAttachment(name, mime, content);
+}
+
 function getRelationMap(req) {
     const {relationMapNoteId, noteIds} = req.body;
 
@@ -340,5 +353,6 @@ module.exports = {
     eraseDeletedNotesNow,
     getDeleteNotesPreview,
     uploadModifiedFile,
-    forceSaveNoteRevision
+    forceSaveNoteRevision,
+    saveNoteAttachment
 };
diff --git a/src/routes/routes.js b/src/routes/routes.js
index cdca32975..f12cbb02b 100644
--- a/src/routes/routes.js
+++ b/src/routes/routes.js
@@ -126,6 +126,7 @@ function register(app) {
     apiRoute(PUT, '/api/notes/:noteId/sort-children', notesApiRoute.sortChildNotes);
     apiRoute(PUT, '/api/notes/:noteId/protect/:isProtected', notesApiRoute.protectNote);
     apiRoute(PUT, '/api/notes/:noteId/type', notesApiRoute.setNoteTypeMime);
+    apiRoute(PUT, '/api/notes/:noteId/attachments/:name', notesApiRoute.saveNoteAttachment);
     apiRoute(GET, '/api/notes/:noteId/revisions', noteRevisionsApiRoute.getNoteRevisions);
     apiRoute(DELETE, '/api/notes/:noteId/revisions', noteRevisionsApiRoute.eraseAllNoteRevisions);
     apiRoute(GET, '/api/notes/:noteId/revisions/:noteRevisionId', noteRevisionsApiRoute.getNoteRevision);